/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.aviary.android.feather.widget;

import android.content.Context;
import android.database.DataSetObserver;
import android.os.Parcelable;
import android.os.SystemClock;
import android.util.AttributeSet;
import android.util.SparseArray;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.SoundEffectConstants;
import android.view.View;
import android.view.ViewDebug;
import android.view.ViewGroup;
import android.view.accessibility.AccessibilityEvent;
import android.widget.Adapter;
import android.widget.GridView;
import android.widget.ListView;
import android.widget.Spinner;

// TODO: Auto-generated Javadoc
/**
 * An AdapterView is a view whose children are determined by an {@link Adapter}.
 * 
 * <p>
 * See {@link ListView}, {@link GridView}, {@link Spinner} and {@link Gallery} for commonly used subclasses of AdapterView.
 * 
 * <div class="special reference">
 * <h3>Developer Guides</h3>
 * <p>
 * For more information about using AdapterView, read the <a href="{@docRoot}guide/topics/ui/binding.html">Binding to Data with
 * AdapterView</a> developer guide.
 * </p>
 * </div>
 * 
 * @param <T>
 *           the generic type
 */
public abstract class AdapterView<T extends Adapter> extends ViewGroup {

	/**
	 * The item view type returned by {@link Adapter#getItemViewType(int)} when the adapter does not want the item's view recycled.
	 */
	public static final int ITEM_VIEW_TYPE_IGNORE = -1;

	/**
	 * The item view type returned by {@link Adapter#getItemViewType(int)} when the item is a header or footer.
	 */
	public static final int ITEM_VIEW_TYPE_HEADER_OR_FOOTER = -2;

	int mFirstPosition = 0;

	/**
	 * The offset in pixels from the top of the AdapterView to the top of the view to select during the next layout.
	 */
	int mSpecificTop;

	/** Position from which to start looking for mSyncRowId. */
	int mSyncPosition;

	/** Row id to look for when data has changed. */
	long mSyncRowId = INVALID_ROW_ID;

	/** Height of the view when mSyncPosition and mSyncRowId where set. */
	long mSyncHeight;

	/** True if we need to sync to mSyncRowId. */
	boolean mNeedSync = false;

	/**
	 * Indicates whether to sync based on the selection or position. Possible values are {@link #SYNC_SELECTED_POSITION} or
	 * {@link #SYNC_FIRST_POSITION}.
	 */
	int mSyncMode;

	/** Our height after the last layout. */
	private int mLayoutHeight;

	/** Sync based on the selected child. */
	static final int SYNC_SELECTED_POSITION = 0;

	/** Sync based on the first child displayed. */
	static final int SYNC_FIRST_POSITION = 1;

	/** Maximum amount of time to spend in {@link #findSyncPosition()}. */
	static final int SYNC_MAX_DURATION_MILLIS = 100;

	/**
	 * Indicates that this view is currently being laid out.
	 */
	boolean mInLayout = false;

	/**
	 * The listener that receives notifications when an item is selected.
	 */
	OnItemSelectedListener mOnItemSelectedListener;

	/**
	 * The listener that receives notifications when an item is clicked.
	 */
	OnItemClickListener mOnItemClickListener;

	/**
	 * The listener that receives notifications when an item is long clicked.
	 */
	OnItemLongClickListener mOnItemLongClickListener;

	/** True if the data has changed since the last layout. */
	boolean mDataChanged;

	/**
	 * The position within the adapter's data set of the item to select during the next layout.
	 */
	int mNextSelectedPosition = INVALID_POSITION;

	/**
	 * The item id of the item to select during the next layout.
	 */
	long mNextSelectedRowId = INVALID_ROW_ID;

	/**
	 * The position within the adapter's data set of the currently selected item.
	 */
	int mSelectedPosition = INVALID_POSITION;

	/**
	 * The item id of the currently selected item.
	 */
	long mSelectedRowId = INVALID_ROW_ID;

	/**
	 * View to show if there are no items to show.
	 */
	private View mEmptyView;

	/**
	 * The number of items in the current adapter.
	 */
	int mItemCount;

	/**
	 * The number of items in the adapter before a data changed event occurred.
	 */
	int mOldItemCount;

	/**
	 * Represents an invalid position. All valid positions are in the range 0 to 1 less than the number of items in the current
	 * adapter.
	 */
	public static final int INVALID_POSITION = -1;

	/** Represents an empty or invalid row id. */
	public static final long INVALID_ROW_ID = Long.MIN_VALUE;

	/** The last selected position we used when notifying. */
	int mOldSelectedPosition = INVALID_POSITION;

	/** The id of the last selected position we used when notifying. */
	long mOldSelectedRowId = INVALID_ROW_ID;

	/**
	 * Indicates what focusable state is requested when calling setFocusable(). In addition to this, this view has other criteria for
	 * actually determining the focusable state (such as whether its empty or the text filter is shown).
	 * 
	 * @see #setFocusable(boolean)
	 * @see #checkFocus()
	 */
	private boolean mDesiredFocusableState;

	/** The m desired focusable in touch mode state. */
	private boolean mDesiredFocusableInTouchModeState;

	/** The m selection notifier. */
	private SelectionNotifier mSelectionNotifier;
	/**
	 * When set to true, calls to requestLayout() will not propagate up the parent hierarchy. This is used to layout the children
	 * during a layout pass.
	 */
	boolean mBlockLayoutRequests = false;

	/**
	 * Instantiates a new adapter view.
	 * 
	 * @param context
	 *           the context
	 */
	public AdapterView( Context context ) {
		super( context );
	}

	/**
	 * Instantiates a new adapter view.
	 * 
	 * @param context
	 *           the context
	 * @param attrs
	 *           the attrs
	 */
	public AdapterView( Context context, AttributeSet attrs ) {
		super( context, attrs );
	}

	/**
	 * Instantiates a new adapter view.
	 * 
	 * @param context
	 *           the context
	 * @param attrs
	 *           the attrs
	 * @param defStyle
	 *           the def style
	 */
	public AdapterView( Context context, AttributeSet attrs, int defStyle ) {
		super( context, attrs, defStyle );
	}

	/**
	 * Interface definition for a callback to be invoked when an item in this AdapterView has been clicked.
	 * 
	 * @see OnItemClickEvent
	 */
	public interface OnItemClickListener {

		/**
		 * Callback method to be invoked when an item in this AdapterView has been clicked.
		 * <p>
		 * Implementers can call getItemAtPosition(position) if they need to access the data associated with the selected item.
		 * 
		 * @param parent
		 *           The AdapterView where the click happened.
		 * @param view
		 *           The view within the AdapterView that was clicked (this will be a view provided by the adapter)
		 * @param position
		 *           The position of the view in the adapter.
		 * @param id
		 *           The row id of the item that was clicked.
		 */
		void onItemClick( AdapterView<?> parent, View view, int position, long id );
	}

	/**
	 * Register a callback to be invoked when an item in this AdapterView has been clicked.
	 * 
	 * @param listener
	 *           The callback that will be invoked.
	 */
	public void setOnItemClickListener( OnItemClickListener listener ) {
		mOnItemClickListener = listener;
	}

	/**
	 * Gets the on item click listener.
	 * 
	 * @return The callback to be invoked with an item in this AdapterView has been clicked, or null id no callback has been set.
	 */
	public final OnItemClickListener getOnItemClickListener() {
		return mOnItemClickListener;
	}

	/**
	 * Call the OnItemClickListener, if it is defined.
	 * 
	 * @param view
	 *           The view within the AdapterView that was clicked.
	 * @param position
	 *           The position of the view in the adapter.
	 * @param id
	 *           The row id of the item that was clicked.
	 * @return True if there was an assigned OnItemClickListener that was called, false otherwise is returned.
	 */
	public boolean performItemClick( View view, int position, long id ) {
		if ( mOnItemClickListener != null ) {
			playSoundEffect( SoundEffectConstants.CLICK );
			if ( view != null ) {
				view.sendAccessibilityEvent( AccessibilityEvent.TYPE_VIEW_CLICKED );
			}
			mOnItemClickListener.onItemClick( this, view, position, id );
			return true;
		}

		return false;
	}

	/**
	 * Interface definition for a callback to be invoked when an item in this view has been clicked and held.
	 * 
	 * @see OnItemLongClickEvent
	 */
	public interface OnItemLongClickListener {

		/**
		 * Callback method to be invoked when an item in this view has been clicked and held.
		 * 
		 * Implementers can call getItemAtPosition(position) if they need to access the data associated with the selected item.
		 * 
		 * @param parent
		 *           The AbsListView where the click happened
		 * @param view
		 *           The view within the AbsListView that was clicked
		 * @param position
		 *           The position of the view in the list
		 * @param id
		 *           The row id of the item that was clicked
		 * 
		 * @return true if the callback consumed the long click, false otherwise
		 */
		boolean onItemLongClick( AdapterView<?> parent, View view, int position, long id );
	}

	/**
	 * Register a callback to be invoked when an item in this AdapterView has been clicked and held.
	 * 
	 * @param listener
	 *           The callback that will run
	 */
	public void setOnItemLongClickListener( OnItemLongClickListener listener ) {
		if ( !isLongClickable() ) {
			setLongClickable( true );
		}
		mOnItemLongClickListener = listener;
	}

	/**
	 * Gets the on item long click listener.
	 * 
	 * @return The callback to be invoked with an item in this AdapterView has been clicked and held, or null id no callback as been
	 *         set.
	 */
	public final OnItemLongClickListener getOnItemLongClickListener() {
		return mOnItemLongClickListener;
	}

	/**
	 * Interface definition for a callback to be invoked when an item in this view has been selected.
	 * 
	 * @see OnItemSelectedEvent
	 */
	public interface OnItemSelectedListener {

		/**
		 * <p>
		 * Callback method to be invoked when an item in this view has been selected. This callback is invoked only when the newly
		 * selected position is different from the previously selected position or if there was no selected item.
		 * </p>
		 * 
		 * Impelmenters can call getItemAtPosition(position) if they need to access the data associated with the selected item.
		 * 
		 * @param parent
		 *           The AdapterView where the selection happened
		 * @param view
		 *           The view within the AdapterView that was clicked
		 * @param position
		 *           The position of the view in the adapter
		 * @param id
		 *           The row id of the item that is selected
		 */
		void onItemSelected( AdapterView<?> parent, View view, int position, long id );

		/**
		 * Callback method to be invoked when the selection disappears from this view. The selection can disappear for instance when
		 * touch is activated or when the adapter becomes empty.
		 * 
		 * @param parent
		 *           The AdapterView that now contains no selected item.
		 */
		void onNothingSelected( AdapterView<?> parent );
	}

	/**
	 * Register a callback to be invoked when an item in this AdapterView has been selected.
	 * 
	 * @param listener
	 *           The callback that will run
	 */
	public void setOnItemSelectedListener( OnItemSelectedListener listener ) {
		mOnItemSelectedListener = listener;
	}

	/**
	 * Gets the on item selected listener.
	 * 
	 * @return the on item selected listener
	 */
	public final OnItemSelectedListener getOnItemSelectedListener() {
		return mOnItemSelectedListener;
	}

	/**
	 * Extra menu information provided to the.
	 * 
	 * {@link android.view.View.OnCreateContextMenuListener#onCreateContextMenu(ContextMenu, View, ContextMenuInfo) } callback when a
	 * context menu is brought up for this AdapterView.
	 */
	public static class AdapterContextMenuInfo implements ContextMenu.ContextMenuInfo {

		/**
		 * Instantiates a new adapter context menu info.
		 * 
		 * @param targetView
		 *           the target view
		 * @param position
		 *           the position
		 * @param id
		 *           the id
		 */
		public AdapterContextMenuInfo( View targetView, int position, long id ) {
			this.targetView = targetView;
			this.position = position;
			this.id = id;
		}

		/**
		 * The child view for which the context menu is being displayed. This will be one of the children of this AdapterView.
		 */
		public View targetView;

		/**
		 * The position in the adapter for which the context menu is being displayed.
		 */
		public int position;

		/**
		 * The row id of the item for which the context menu is being displayed.
		 */
		public long id;
	}

	/**
	 * Returns the adapter currently associated with this widget.
	 * 
	 * @return The adapter used to provide this view's content.
	 */
	public abstract T getAdapter();

	/**
	 * Sets the adapter that provides the data and the views to represent the data in this widget.
	 * 
	 * @param adapter
	 *           The adapter to use to create this view's content.
	 */
	public abstract void setAdapter( T adapter );

	/**
	 * This method is not supported and throws an UnsupportedOperationException when called.
	 * 
	 * @param child
	 *           Ignored.
	 */
	@Override
	public void addView( View child ) {
		throw new UnsupportedOperationException( "addView(View) is not supported in AdapterView" );
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException when called.
	 * 
	 * @param child
	 *           Ignored.
	 * @param index
	 *           Ignored.
	 */
	@Override
	public void addView( View child, int index ) {
		throw new UnsupportedOperationException( "addView(View, int) is not supported in AdapterView" );
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException when called.
	 * 
	 * @param child
	 *           Ignored.
	 * @param params
	 *           Ignored.
	 */
	@Override
	public void addView( View child, LayoutParams params ) {
		throw new UnsupportedOperationException( "addView(View, LayoutParams) " + "is not supported in AdapterView" );
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException when called.
	 * 
	 * @param child
	 *           Ignored.
	 * @param index
	 *           Ignored.
	 * @param params
	 *           Ignored.
	 */
	@Override
	public void addView( View child, int index, LayoutParams params ) {
		throw new UnsupportedOperationException( "addView(View, int, LayoutParams) " + "is not supported in AdapterView" );
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException when called.
	 * 
	 * @param child
	 *           Ignored.
	 */
	@Override
	public void removeView( View child ) {
		throw new UnsupportedOperationException( "removeView(View) is not supported in AdapterView" );
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException when called.
	 * 
	 * @param index
	 *           Ignored.
	 */
	@Override
	public void removeViewAt( int index ) {
		throw new UnsupportedOperationException( "removeViewAt(int) is not supported in AdapterView" );
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException when called.
	 * 
	 */
	@Override
	public void removeAllViews() {
		throw new UnsupportedOperationException( "removeAllViews() is not supported in AdapterView" );
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see android.view.ViewGroup#onLayout(boolean, int, int, int, int)
	 */
	@Override
	protected void onLayout( boolean changed, int left, int top, int right, int bottom ) {
		mLayoutHeight = getHeight();
	}

	/**
	 * Return the position of the currently selected item within the adapter's data set.
	 * 
	 * @return int Position (starting at 0), or {@link #INVALID_POSITION} if there is nothing selected.
	 */
	@ViewDebug.CapturedViewProperty
	public int getSelectedItemPosition() {
		return mNextSelectedPosition;
	}

	/**
	 * Gets the selected item id.
	 * 
	 * @return The id corresponding to the currently selected item, or {@link #INVALID_ROW_ID} if nothing is selected.
	 */
	@ViewDebug.CapturedViewProperty
	public long getSelectedItemId() {
		return mNextSelectedRowId;
	}

	/**
	 * Gets the selected view.
	 * 
	 * @return The view corresponding to the currently selected item, or null if nothing is selected
	 */
	public abstract View getSelectedView();

	/**
	 * Gets the selected item.
	 * 
	 * @return The data corresponding to the currently selected item, or null if there is nothing selected.
	 */
	public Object getSelectedItem() {
		T adapter = getAdapter();
		int selection = getSelectedItemPosition();
		if ( adapter != null && adapter.getCount() > 0 && selection >= 0 ) {
			return adapter.getItem( selection );
		} else {
			return null;
		}
	}

	/**
	 * Gets the count.
	 * 
	 * @return The number of items owned by the Adapter associated with this AdapterView. (This is the number of data items, which
	 *         may be larger than the number of visible views.)
	 */
	@ViewDebug.CapturedViewProperty
	public int getCount() {
		return mItemCount;
	}

	/**
	 * Get the position within the adapter's data set for the view, where view is a an adapter item or a descendant of an adapter
	 * item.
	 * 
	 * @param view
	 *           an adapter item, or a descendant of an adapter item. This must be visible in this AdapterView at the time of the
	 *           call.
	 * @return the position within the adapter's data set of the view, or {@link #INVALID_POSITION} if the view does not correspond
	 *         to a list item (or it is not currently visible).
	 */
	public int getPositionForView( View view ) {
		View listItem = view;
		try {
			View v;
			while ( !( v = (View) listItem.getParent() ).equals( this ) ) {
				listItem = v;
			}
		} catch ( ClassCastException e ) {
			// We made it up to the window without find this list view
			return INVALID_POSITION;
		}

		// Search the children for the list item
		final int childCount = getChildCount();
		for ( int i = 0; i < childCount; i++ ) {
			if ( getChildAt( i ).equals( listItem ) ) {
				return mFirstPosition + i;
			}
		}

		// Child not found!
		return INVALID_POSITION;
	}

	/**
	 * Returns the position within the adapter's data set for the first item displayed on screen.
	 * 
	 * @return The position within the adapter's data set
	 */
	public int getFirstVisiblePosition() {
		return mFirstPosition;
	}

	/**
	 * Returns the position within the adapter's data set for the last item displayed on screen.
	 * 
	 * @return The position within the adapter's data set
	 */
	public int getLastVisiblePosition() {
		return mFirstPosition + getChildCount() - 1;
	}

	/**
	 * Sets the currently selected item. To support accessibility subclasses that override this method must invoke the overriden
	 * super method first.
	 * 
	 * @param position
	 *           Index (starting at 0) of the data item to be selected.
	 */
	public abstract void setSelection( int position );

	/**
	 * Sets the view to show if the adapter is empty.
	 * 
	 * @param emptyView
	 *           the new empty view
	 */
	public void setEmptyView( View emptyView ) {
		mEmptyView = emptyView;

		final T adapter = getAdapter();
		final boolean empty = ( ( adapter == null ) || adapter.isEmpty() );
		updateEmptyStatus( empty );
	}

	/**
	 * When the current adapter is empty, the AdapterView can display a special view call the empty view. The empty view is used to
	 * provide feedback to the user that no data is available in this AdapterView.
	 * 
	 * @return The view to show if the adapter is empty.
	 */
	public View getEmptyView() {
		return mEmptyView;
	}

	/**
	 * Indicates whether this view is in filter mode. Filter mode can for instance be enabled by a user when typing on the keyboard.
	 * 
	 * @return True if the view is in filter mode, false otherwise.
	 */
	boolean isInFilterMode() {
		return false;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see android.view.View#setFocusable(boolean)
	 */
	@Override
	public void setFocusable( boolean focusable ) {
		final T adapter = getAdapter();
		final boolean empty = adapter == null || adapter.getCount() == 0;

		mDesiredFocusableState = focusable;
		if ( !focusable ) {
			mDesiredFocusableInTouchModeState = false;
		}

		super.setFocusable( focusable && ( !empty || isInFilterMode() ) );
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see android.view.View#setFocusableInTouchMode(boolean)
	 */
	@Override
	public void setFocusableInTouchMode( boolean focusable ) {
		final T adapter = getAdapter();
		final boolean empty = adapter == null || adapter.getCount() == 0;

		mDesiredFocusableInTouchModeState = focusable;
		if ( focusable ) {
			mDesiredFocusableState = true;
		}

		super.setFocusableInTouchMode( focusable && ( !empty || isInFilterMode() ) );
	}

	/**
	 * Check focus.
	 */
	void checkFocus() {
		final T adapter = getAdapter();
		final boolean empty = adapter == null || adapter.getCount() == 0;
		final boolean focusable = !empty || isInFilterMode();
		// The order in which we set focusable in touch mode/focusable may matter
		// for the client, see View.setFocusableInTouchMode() comments for more
		// details
		super.setFocusableInTouchMode( focusable && mDesiredFocusableInTouchModeState );
		super.setFocusable( focusable && mDesiredFocusableState );
		if ( mEmptyView != null ) {
			updateEmptyStatus( ( adapter == null ) || adapter.isEmpty() );
		}
	}

	/**
	 * Update the status of the list based on the empty parameter. If empty is true and we have an empty view, display it. In all the
	 * other cases, make sure that the listview is VISIBLE and that the empty view is GONE (if it's not null).
	 * 
	 * @param empty
	 *           the empty
	 */
	private void updateEmptyStatus( boolean empty ) {
		if ( isInFilterMode() ) {
			empty = false;
		}

		if ( empty ) {
			if ( mEmptyView != null ) {
				mEmptyView.setVisibility( View.VISIBLE );
				setVisibility( View.GONE );
			} else {
				// If the caller just removed our empty view, make sure the list view is visible
				setVisibility( View.VISIBLE );
			}

			// We are now GONE, so pending layouts will not be dispatched.
			// Force one here to make sure that the state of the list matches
			// the state of the adapter.
			if ( mDataChanged ) {
				this.onLayout( false, getLeft(), getTop(), getRight(), getBottom() );
			}
		} else {
			if ( mEmptyView != null ) mEmptyView.setVisibility( View.GONE );
			setVisibility( View.VISIBLE );
		}
	}

	/**
	 * Gets the data associated with the specified position in the list.
	 * 
	 * @param position
	 *           Which data to get
	 * @return The data associated with the specified position in the list
	 */
	public Object getItemAtPosition( int position ) {
		T adapter = getAdapter();
		return ( adapter == null || position < 0 ) ? null : adapter.getItem( position );
	}

	/**
	 * Gets the item id at position.
	 * 
	 * @param position
	 *           the position
	 * @return the item id at position
	 */
	public long getItemIdAtPosition( int position ) {
		T adapter = getAdapter();
		return ( adapter == null || position < 0 ) ? INVALID_ROW_ID : adapter.getItemId( position );
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see android.view.View#setOnClickListener(android.view.View.OnClickListener)
	 */
	@Override
	public void setOnClickListener( OnClickListener l ) {
		throw new RuntimeException( "Don't call setOnClickListener for an AdapterView. "
				+ "You probably want setOnItemClickListener instead" );
	}

	/**
	 * Override to prevent freezing of any views created by the adapter.
	 * 
	 * @param container
	 *           the container
	 */
	@Override
	protected void dispatchSaveInstanceState( SparseArray<Parcelable> container ) {
		dispatchFreezeSelfOnly( container );
	}

	/**
	 * Override to prevent thawing of any views created by the adapter.
	 * 
	 * @param container
	 *           the container
	 */
	@Override
	protected void dispatchRestoreInstanceState( SparseArray<Parcelable> container ) {
		dispatchThawSelfOnly( container );
	}

	/**
	 * An asynchronous update interface for receiving notifications about AdapterDataSet information as the AdapterDataSet is
	 * constructed.
	 */
	class AdapterDataSetObserver extends DataSetObserver {

		/** The m instance state. */
		private Parcelable mInstanceState = null;

		/*
		 * (non-Javadoc)
		 * 
		 * @see android.database.DataSetObserver#onChanged()
		 */
		@Override
		public void onChanged() {
			mDataChanged = true;
			mOldItemCount = mItemCount;
			mItemCount = getAdapter().getCount();

			// Detect the case where a cursor that was previously invalidated has
			// been repopulated with new data.
			if ( AdapterView.this.getAdapter().hasStableIds() && mInstanceState != null && mOldItemCount == 0 && mItemCount > 0 ) {
				AdapterView.this.onRestoreInstanceState( mInstanceState );
				mInstanceState = null;
			} else {
				rememberSyncState();
			}
			checkFocus();
			requestLayout();
		}

		/*
		 * (non-Javadoc)
		 * 
		 * @see android.database.DataSetObserver#onInvalidated()
		 */
		@Override
		public void onInvalidated() {
			mDataChanged = true;

			if ( AdapterView.this.getAdapter().hasStableIds() ) {
				// Remember the current state for the case where our hosting activity is being
				// stopped and later restarted
				mInstanceState = AdapterView.this.onSaveInstanceState();
			}

			// Data is invalid so we should reset our state
			mOldItemCount = mItemCount;
			mItemCount = 0;
			mSelectedPosition = INVALID_POSITION;
			mSelectedRowId = INVALID_ROW_ID;
			mNextSelectedPosition = INVALID_POSITION;
			mNextSelectedRowId = INVALID_ROW_ID;
			mNeedSync = false;

			checkFocus();
			requestLayout();
		}

		/**
		 * This method is called when information about an AdapterDataSet which was previously requested using an asynchronous
		 * interface becomes available.
		 */
		public void clearSavedState() {
			mInstanceState = null;
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see android.view.View#onDetachedFromWindow()
	 */
	@Override
	protected void onDetachedFromWindow() {
		super.onDetachedFromWindow();
		removeCallbacks( mSelectionNotifier );
	}

	/**
	 * The Class SelectionNotifier.
	 */
	private class SelectionNotifier implements Runnable {

		/*
		 * (non-Javadoc)
		 * 
		 * @see java.lang.Runnable#run()
		 */
		public void run() {
			if ( mDataChanged ) {
				// Data has changed between when this SelectionNotifier
				// was posted and now. We need to wait until the AdapterView
				// has been synched to the new data.
				if ( getAdapter() != null ) {
					post( this );
				}
			} else {
				fireOnSelected();
			}
		}
	}

	/**
	 * Selection changed.
	 */
	void selectionChanged() {
		if ( mOnItemSelectedListener != null ) {
			if ( mInLayout || mBlockLayoutRequests ) {
				// If we are in a layout traversal, defer notification
				// by posting. This ensures that the view tree is
				// in a consistent state and is able to accomodate
				// new layout or invalidate requests.
				if ( mSelectionNotifier == null ) {
					mSelectionNotifier = new SelectionNotifier();
				}
				post( mSelectionNotifier );
			} else {
				fireOnSelected();
			}
		}

		// we fire selection events here not in View
		if ( mSelectedPosition != ListView.INVALID_POSITION && isShown() && !isInTouchMode() ) {
			sendAccessibilityEvent( AccessibilityEvent.TYPE_VIEW_SELECTED );
		}
	}

	/**
	 * Fire on selected.
	 */
	private void fireOnSelected() {
		if ( mOnItemSelectedListener == null ) return;

		int selection = this.getSelectedItemPosition();
		if ( selection >= 0 ) {
			View v = getSelectedView();
			mOnItemSelectedListener.onItemSelected( this, v, selection, getAdapter().getItemId( selection ) );
		} else {
			mOnItemSelectedListener.onNothingSelected( this );
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see android.view.View#dispatchPopulateAccessibilityEvent(android.view.accessibility.AccessibilityEvent)
	 */
	@Override
	public boolean dispatchPopulateAccessibilityEvent( AccessibilityEvent event ) {
		View selectedView = getSelectedView();
		if ( selectedView != null && selectedView.getVisibility() == VISIBLE
				&& selectedView.dispatchPopulateAccessibilityEvent( event ) ) {
			return true;
		}
		return false;
	}

	/**
	 * Checks if is scrollable for accessibility.
	 * 
	 * @return true, if is scrollable for accessibility
	 */
	private boolean isScrollableForAccessibility() {
		T adapter = getAdapter();
		if ( adapter != null ) {
			final int itemCount = adapter.getCount();
			return itemCount > 0 && ( getFirstVisiblePosition() > 0 || getLastVisiblePosition() < itemCount - 1 );
		}
		return false;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see android.view.ViewGroup#canAnimate()
	 */
	@Override
	protected boolean canAnimate() {
		return super.canAnimate() && mItemCount > 0;
	}

	/**
	 * Handle data changed.
	 */
	void handleDataChanged() {
		final int count = mItemCount;
		boolean found = false;

		if ( count > 0 ) {

			int newPos;

			// Find the row we are supposed to sync to
			if ( mNeedSync ) {
				// Update this first, since setNextSelectedPositionInt inspects
				// it
				mNeedSync = false;

				// See if we can find a position in the new data with the same
				// id as the old selection
				newPos = findSyncPosition();
				if ( newPos >= 0 ) {
					// Verify that new selection is selectable
					int selectablePos = lookForSelectablePosition( newPos, true );
					if ( selectablePos == newPos ) {
						// Same row id is selected
						setNextSelectedPositionInt( newPos );
						found = true;
					}
				}
			}
			if ( !found ) {
				// Try to use the same position if we can't find matching data
				newPos = getSelectedItemPosition();

				// Pin position to the available range
				if ( newPos >= count ) {
					newPos = count - 1;
				}
				if ( newPos < 0 ) {
					newPos = 0;
				}

				// Make sure we select something selectable -- first look down
				int selectablePos = lookForSelectablePosition( newPos, true );
				if ( selectablePos < 0 ) {
					// Looking down didn't work -- try looking up
					selectablePos = lookForSelectablePosition( newPos, false );
				}
				if ( selectablePos >= 0 ) {
					setNextSelectedPositionInt( selectablePos );
					checkSelectionChanged();
					found = true;
				}
			}
		}
		if ( !found ) {
			// Nothing is selected
			mSelectedPosition = INVALID_POSITION;
			mSelectedRowId = INVALID_ROW_ID;
			mNextSelectedPosition = INVALID_POSITION;
			mNextSelectedRowId = INVALID_ROW_ID;
			mNeedSync = false;
			checkSelectionChanged();
		}
	}

	/**
	 * Check selection changed.
	 */
	void checkSelectionChanged() {
		if ( ( mSelectedPosition != mOldSelectedPosition ) || ( mSelectedRowId != mOldSelectedRowId ) ) {
			selectionChanged();
			mOldSelectedPosition = mSelectedPosition;
			mOldSelectedRowId = mSelectedRowId;
		}
	}

	/**
	 * Searches the adapter for a position matching mSyncRowId. The search starts at mSyncPosition and then alternates between moving
	 * up and moving down until 1) we find the right position, or 2) we run out of time, or 3) we have looked at every position
	 * 
	 * @return Position of the row that matches mSyncRowId, or {@link #INVALID_POSITION} if it can't be found
	 */
	int findSyncPosition() {
		int count = mItemCount;

		if ( count == 0 ) {
			return INVALID_POSITION;
		}

		long idToMatch = mSyncRowId;
		int seed = mSyncPosition;

		// If there isn't a selection don't hunt for it
		if ( idToMatch == INVALID_ROW_ID ) {
			return INVALID_POSITION;
		}

		// Pin seed to reasonable values
		seed = Math.max( 0, seed );
		seed = Math.min( count - 1, seed );

		long endTime = SystemClock.uptimeMillis() + SYNC_MAX_DURATION_MILLIS;

		long rowId;

		// first position scanned so far
		int first = seed;

		// last position scanned so far
		int last = seed;

		// True if we should move down on the next iteration
		boolean next = false;

		// True when we have looked at the first item in the data
		boolean hitFirst;

		// True when we have looked at the last item in the data
		boolean hitLast;

		// Get the item ID locally (instead of getItemIdAtPosition), so
		// we need the adapter
		T adapter = getAdapter();
		if ( adapter == null ) {
			return INVALID_POSITION;
		}

		while ( SystemClock.uptimeMillis() <= endTime ) {
			rowId = adapter.getItemId( seed );
			if ( rowId == idToMatch ) {
				// Found it!
				return seed;
			}

			hitLast = last == count - 1;
			hitFirst = first == 0;

			if ( hitLast && hitFirst ) {
				// Looked at everything
				break;
			}

			if ( hitFirst || ( next && !hitLast ) ) {
				// Either we hit the top, or we are trying to move down
				last++;
				seed = last;
				// Try going up next time
				next = false;
			} else if ( hitLast || ( !next && !hitFirst ) ) {
				// Either we hit the bottom, or we are trying to move up
				first--;
				seed = first;
				// Try going down next time
				next = true;
			}

		}

		return INVALID_POSITION;
	}

	/**
	 * Find a position that can be selected (i.e., is not a separator).
	 * 
	 * @param position
	 *           The starting position to look at.
	 * @param lookDown
	 *           Whether to look down for other positions.
	 * @return The next selectable position starting at position and then searching either up or down. Returns
	 *         {@link #INVALID_POSITION} if nothing can be found.
	 */
	int lookForSelectablePosition( int position, boolean lookDown ) {
		return position;
	}

	/**
	 * Utility to keep mSelectedPosition and mSelectedRowId in sync.
	 * 
	 * @param position
	 *           Our current position
	 */
	void setSelectedPositionInt( int position ) {
		mSelectedPosition = position;
		mSelectedRowId = getItemIdAtPosition( position );
	}

	/**
	 * Utility to keep mNextSelectedPosition and mNextSelectedRowId in sync.
	 * 
	 * @param position
	 *           Intended value for mSelectedPosition the next time we go through layout
	 */
	void setNextSelectedPositionInt( int position ) {
		mNextSelectedPosition = position;
		mNextSelectedRowId = getItemIdAtPosition( position );
		// If we are trying to sync to the selection, update that too
		if ( mNeedSync && mSyncMode == SYNC_SELECTED_POSITION && position >= 0 ) {
			mSyncPosition = position;
			mSyncRowId = mNextSelectedRowId;
		}
	}

	/**
	 * Remember enough information to restore the screen state when the data has changed.
	 * 
	 */
	void rememberSyncState() {
		if ( getChildCount() > 0 ) {
			mNeedSync = true;
			mSyncHeight = mLayoutHeight;
			if ( mSelectedPosition >= 0 ) {
				// Sync the selection state
				View v = getChildAt( mSelectedPosition - mFirstPosition );
				mSyncRowId = mNextSelectedRowId;
				mSyncPosition = mNextSelectedPosition;
				if ( v != null ) {
					mSpecificTop = v.getTop();
				}
				mSyncMode = SYNC_SELECTED_POSITION;
			} else {
				// Sync the based on the offset of the first view
				View v = getChildAt( 0 );
				T adapter = getAdapter();
				if ( mFirstPosition >= 0 && mFirstPosition < adapter.getCount() ) {
					mSyncRowId = adapter.getItemId( mFirstPosition );
				} else {
					mSyncRowId = NO_ID;
				}
				mSyncPosition = mFirstPosition;
				if ( v != null ) {
					mSpecificTop = v.getTop();
				}
				mSyncMode = SYNC_FIRST_POSITION;
			}
		}
	}
}
